This invention relates to small angular displacement measurement apparatus and more particularly to a small angle test apparatus for use in obtaining known milliradian angular displacement with a high degree of accuracy.
High frequency dynamic precision measurement of small angular displacement is not now available. For example, angular displacement vibration sensors having 1 milliradian full-scale sensing capability are available but must be calibrated dynamically for scale factor prior to usage in the system wherein they are required. When high degrees of accuracy are required of such sensors, such as 0.1 percent of full-scale, a calibration reference is needed having sensitivity capability down to one microadian.
Static or very low frequency calibration of angular output from angular motion sensors designed to detect minute angular motion may be obtained using a beam autocollimator and an associated mirror for reflecting a beam through an angle according to sensor angular motion. Autocollimators are structurally complex and quite expensive.
A simplified and inexpensive calibration apparatus is therefore needed for determining minute static and dynamic angular motion.